This invention pertains to fluidized bed type catalytic reactors. It pertains particularly to such reactors having an addition/withdrawal conduit for particulate catalyst extending through a flow distribution grid plate located in the reactor lower portion, with the conduit being sealably attached to the grid plate by a bellows type expansion unit.
A known pressurizable ebullated bed catalytic reactor adapted for operation at elevated temperature and pressure conditions and having a lower grid plate for supporting a bed of particulate catalyst, with the grid plate containing multiple riser tubes each covered by a bubble cap for upward fluid flow is generally disclosed by U.S. Pat. No. 3,475,134 to Weber et al. Particulate catalyst is periodically added to and withdrawn from the reactor ebullated bed through an elongated conduit extending upwardly through the reactor lower head and through the grid plate. From past operating experience, such conduits have been a problem because they sometimes fail prematurely near the grid plate due to severe erosion by the randomly moving catalyst particles in the ebullated bed. Such erosion by the catalyst particles is apparently caused by hydrogen gas passing at high velocity through gaps which sometimes occur in a split flange type seal which is usually used around the conduit above the grid plate, for permitting necessary vertical thermal expansion movement of the conduit relative to the grid plate. Because of these undesired erosion problems in such reactors, an improved configuration for sealably attaching the catalyst addition/withdrawal conduit to the reactor grid plate is needed.